NCTUns tool for wireless vehicular communication network researches

Abstract

Several goals such as improving road safety and increasing transport efficiency are being pursued in intelligent transportation systems (ITS). Wireless vehicular communication is one technology to achieve these goals. Conducting vehicular experiments on the roads is an approach to studying the effectiveness of wireless vehicular communication. However, such an approach is costly, hard-to-control (repeat), dangerous, and infeasible when many vehicles and people are involved in the field trial. In contrast, the simulation approach does not have these problems. It is a very useful approach and complements the field trial approach. This paper presents NCTUns, an open source integrated simulation platform, for wireless vehicular communication network researches. This tool tightly integrates network and traffic simulations and provides a fast feedback loop between them. Therefore, a simulated vehicle can quickly change its driving behavior such as moving speed and direction when it receives a message from the wireless vehicular communication network. This capability is required by several novel ITS applications such as active collision avoidance systems. In this paper, we present the design, implementation, validation, and performance of this tool.

Introduction

Intelligent transportation systems (ITS) has become an attractive research field for many years. Among many technologies proposed for ITS, wireless vehicular communication, covering vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), and vehicle-to-person (V2P) communication, aims to increase road safety and transport efficiency and provide ubiquitous wireless connectivity to the Internet. With the assistances from these different means of communication, drivers and pedestrians can quickly obtain useful and/or emergent traffic information on the roads at a low cost. For this reason, wireless vehicular communication has become a very important technology for intelligent transportation systems.

The IEEE 802.11p [1] and IEEE 1609 draft standards [2], [3], [4], [5] have been proposed as a networking technology for vehicular environments. ITS applications based on this new technology must be thoroughly tested and evaluated before being deployed on the roads. This means that many experiments under different parameters settings, configurations, scenarios, and conditions must be performed to verify the feasibility and effectiveness of an application and the used networking technology in the real-life environment. According to the results obtained from experiments, the designs of the application and the used networking technology might need to be revised many times before acceptable performances can be achieved.

A field trial of wireless vehicular communication usually involves a large number of vehicles and people (drivers and computer operators) for generating meaningful results. Conducting such field trials is very costly because many vehicles need to be rented (or purchased), many communication equipments need to be purchased, and many experimenters need to be employed for conducting the field trials. Sometimes, during a field trial with a specifically-designed high-speed scenario, the experimenters may even have to face potential dangers such as collisions with vehicles or pedestrians. Besides, it is very difficult to accurately control and repeat a field trial on the roads, which is bad for debugging the problems and improving the performances of a new protocol or application. Given these problems, it is highly desirable to use software simulation to perform indoor function testing and performance evaluations prior to conducting field trials.

To study wireless vehicular communication networks, a simulator must be able to simulate both communication/network protocols and microscopic vehicular movements. The two requirements are not new and such capabilities are already provided by existing network simulators or traffic simulators, respectively. Regarding network simulators, they are usually used to test the functions and evaluate the performances of network protocols and applications under various network conditions. One can use them to test how his/her protocols (e.g., routing protocols, medium access control protocols, or transport protocols) and applications (e.g., HTTP, FTP, or VoIP) would perform under various network conditions. On the other hand, traffic simulators are usually used to simulate drivers’ driving behavior (e.g., car following, lane changing, overtaking, etc.) on different kinds of road networks (e.g., freeways, urban areas, etc.). One usually uses them in the research areas of transportation engineering, such as transportation planning and traffic engineering.

Mostly, a network simulator is dedicated only to the studies of network protocols and applications and a traffic simulator is only dedicated to the studies of transportation engineering. To study advanced ITS applications, however, a simulation platform must be able to simulate both network and traffic simultaneously and provide a fast feedback loop between them. For example, some intelligent transportation systems aim to add information and communication technologies into transport infrastructures and vehicles to improve safety and reduce vehicle wear, transportation time, and fuel consumption. For these applications, the driving behavior of a vehicle may need to be changed after receiving a message from the wireless vehicular communication network. To study these applications, a simulation platform must tightly integrate both network and traffic simulations and provide a fast feedback loop between them.

In this paper, we present an integrated simulation platform, called NCTUns, for wireless vehicular communication networks research. NCTUns 1.0 [6] was originally developed as a network simulator with unique network simulation capabilities. Later on, NCTUns 5.0 [7] incorporates traffic simulation (e.g., road network construction and microscopic vehicle mobility models) with its existing network simulation, tightly integrates them together, and provides a fast feedback loop between them. With these capabilities, NCTUns now is a useful simulation platform for wireless vehicular communication network researches.

The rest of the paper is organized as follows. In Section 2, we survey related work that combines the capabilities from both a network simulator and a traffic simulator. In Section 3, we present the design and implementation of NCTUns, including platform architecture, supported road types, vehicle movement controls, application program interfaces, and network protocol simulations. In Section 4, we validate the mobility control of vehicles on NCTUns with mathematical models based on Newton’s laws of motion. In Section 5, the scalability performances of NCTUns are evaluated. In Section 6, we present three usage examples of NCTUns. In Section 7, we discuss ongoing work for the next release of NCTUns. Finally, we conclude the paper in Section 8.